Effect of Dapsone on HbA1c Levels Clinical and Experimental Dermatology

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• In order to highlight an uncommon potential adverse effect, the authors present the case of a 50-year-old man with a long history of suboptimally controlled type 1 diabetes mellitus who was treated with dapsone for dermatitis herpetiformis. The patient had a baseline hemoglobin A1c (HbA1c) stable around 8.1% for several years despite his insulin regimen (for reference, goal HbA1c in diabetics is <6.5%). Within 4 months of starting dapsone, the HbA1c decreased to 4.2% without any changes in lifestyle, diet, or insulin regimen.

• The authors discuss mechanisms for this falsely low HbA1c in patients taking dapsone. These include a reduced erythrocyte lifespan, thus reducing the amount of time each erythrocyte is exposed to blood glucose and falsely lowering the HbA1c reading, as well as oxidation of hemoglobin to methemoglobin, which may interfere with the HbA1c assay. In patients on dapsone where HbA1c is unreliable, tests for glucose monitoring that can be more useful include fructosamine assay, glycated albumin, serum 1,5-anhydroglucitol assay, capillary blood glucose, and interstitial glucose sensors. Educating diabetic patients on this potential adverse effect of dapsone is important to ensure that glucose control can be monitored and managed safely and appropriately.

– Caroline K. Crabtree, MD

Abstract 

We would like to highlight an important clinical lesson regarding a drug‐related side effect of dapsone use.

Clinical and Experimental Dermatology

HbA1c Levels: Falsely Low in a Patient Taking Dapsone

Clin Exp Dermatol 2020 Jun 23;[EPub Ahead of Print], IR Spring, C Ilangaratne, S Walsh 

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Benjamin Hidalgo-Matlock
Skin Care Physicians of Costa Rica

Clinica Victoria en San Pedro: 4000-1054
Momentum Escazu: 2101-9574

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